An original database compiled by the authors on volatile components of mineral-hosted fluid inclusions currently includes 12 470 analyses from 480 publications and was used to calculate the average gas phase composition of fluids that formed hydrothermal deposits throughout the Earth’s geological evolution, from the Archean to Cenozoic. The paper reviews the methods used in the study, their potential errors, and limitations. Characteristics of the gas composition of fluids are traced for more than 300 ore deposits of Au, Sn, W, Cu, Cu, Pb, Zn, Sb, Mo, and U. The dominant volatile component of natural mineralizing fluids in the Earth’s crust is carbon dioxide, regardless of the geologic age. The fluids contain subordinate amounts of reduced carbon species (methane) and nitrogen, as well as minor amounts of hydrogen sulfide and some other gases. The Cenozoic fluids commonly contain more nitrogen than methane. These relations are occasionally also found in the Precambrian fluids. The CO2/CH4 ratio as an indicator of the redox state of the system notably increased over the Earth’s geological history.

Based on the mean contents of elements and their standard deviations estimated in the first part of this contribution (Naumov et al., 2023), we compared in detail the geodynamic settings distinguished earlier. In order to compare the compositions of mafic melts, a correction was introduced for changes related to the fractionation of the main minerals. Using numerical criteria, the elements were arranged in a sequence of the increasing degree of compatibility during melting and crystallization, and regular variations in element contents normalized to the mean composition of oceanic-island melts were distinguished. The melts of mid-oceanic ridges show a monotonous increase in normalized contents from the most incompatible (Cs, Ba, U, La, etc.) to compatible elements (Sc, Ni, and Cr). The settings of convergent plate boundaries show relative enrichment in the most incompatible elements and significant negative Ta−Nb anomalies relative to neighboring elements. The magmas of continental rifts show the most significant enrichment in the most incompatible elements, as well as Pb, Li, and some other elements. Indicator element ratios showing significant variations between the settings were distinguished for mafic melts. Some element ratios are almost identical (within observed variations) in mafic melts from all the settings. The mean element ratios in mafic, intermediate, and silicic magmas show three types of behavior. Some ratios (including the canonic ratios Nb/Ta, Zr/Hf, etc.) in intermediate and silicic magmas are inherited from the composition of mafic melts. Some ratios show irregular changes from mafic to silicic melts (Sr/Cr, F/Th, etc.). Some other ratios change monotonously and significantly in the sequence from mafic to silicic melts (Ni/Yb, Lu/P, etc.). The variations in element ratios are related to the crystallization differentiation of melts and contributions of geochemically contrasting reservoirs.

We analyzed published datasets relating to the composition of glasses from melt inclusions in minerals of volcanics from the Eastern Volcanic Belt and Sredinny Range of Kamchatka. A significant difference was found between the distribution of silica concentration in the rocks and melts: intermediate and basic compositions are most common among the rocks, whereas the glasses in melt inclusions are predominantly acidic. The distribution of major and trace elements was analyzed. It was shown that the contents of some elements are environment-specific (e.g., Nb and light REEs). We identified trace element ratios in melts that most strongly correlate with the geodynamic setting.

Data from our original database, which includes more than 2 600 000 analyses for 75 elements of mineral-hosted melt inclusions and quench glasses in volcanic rocks, are generalized to calculate the mean concentrations of major, volatile, ore, and trace elements in magmatic melts from the following dominant geodynamic environments: (I) spreading zones of oceanic plates (mid-oceanic ridges), (II) environments affected by mantle plumes in oceanic plates (oceanic islands and lava plateaus), (III, IV) environments related to subduction processes (III is zones of arc magmatism on the oceanic crust, and IV is zones of magmatism in active continental margins in which magma-generating processes involve the continental crust), (V) environments of continental rifts and areas with continental hotspots, and (VI) environments of backarc spreading. A histogram of SiO2 distribution in natural magmatic melts shows a bimodal distribution: one of the maxima falls onto SiO2 concentrations of 50–52 wt

Data from our original database, which includes more than 2 600 000 analyses for 75 elements of mineral-hosted melt inclusions and quench glasses in volcanic rocks, are generalized to calculate the mean concentrations of major, volatile, ore, and trace elements in magmatic melts from the following dominant geodynamic environments: (I) spreading zones of oceanic plates (mid-oceanic ridges), (II) environments affected by mantle plumes in oceanic plates (oceanic islands and lava plateaus), (III, IV) environments related to subduction processes (III is zones of arc magmatism on the oceanic crust, and IV is zones of magmatism in active continental margins in which magma-generating processes involve the continental crust), (V) environments of continental rifts and areas with continental hotspots, and (VI) environments of backarc spreading. A histogram of SiO2 distribution in natural magmatic melts shows a bimodal distribution: one of the maxima falls onto SiO2 concentrations of 50–52 wt % and the other onto 72–76 wt %. The most widely spread melts contain 62–66 wt % SiO2. Mean temperatures and pressures are calculated for each of the environments. The normalized multielemental patterns presented for environments I through VI show the ratios of the mean concentrations of elements in magmatic melts of mafic, intermediate, and felsic composition to the concentrations in the primitive mantle. Mean ratios of incompatible, trace, and volatile components (H2O/Ce, K2O/Cl, Nb/U, Ba/Rb, Ce/Pb, etc.) are evaluated for the melts of each of the environments. The variations in these ratios are calculated, and it is demonstrated that the ratios of incompatible elements are mostly statistically significantly different in the different environments. The differences are particularly significant between the ratios of the most differently incompatible elements (e.g., Nb/Yb) and some ratios involving volatile components (e.g., K2O/H2O).

This paper reviews data from numerous publications focused on the physicochemical parameters and chemical composition of ore-forming fluids from orogenic gold deposits formed during various geological epochs. The paper presents analysis of the distribution of the principal parameters of mineralizing fluids depending on the age of the mineralization. Some parameters of the fluids (their salinity and pressure) at orogenic gold deposits are demonstrated to systematically vary from older (median salinity 6.1 wt.%, median pressure 1680 bar) to younger (median salinity 3.6 wt.%, median pressure 1305 bar) deposits. The detected statistically significant differences between some parameters of mineralizing fluids at orogenic gold deposits are principally new information. The parameters at which mineralization of various age was formed are demonstrated to pertain to different depth levels of similar mineralization-forming systems. The fluid parameters of the most ancient deposits (which are mostly deeply eroded) correspond to the deepest levels of orogenic fluid systems. Hence, the detected differences in the salinity and pressure of the mineralizing fluids at orogenic deposits of different age reflect the vertical zoning of the mineralizing fluid systems.

The paper reviews and summarizes data on the physicochemical parameters and chemical features of mineralizing fluids at porphyry deposits of the Cu–Mo–Au system. The calculated average values and ranges of parameters of the fluids in mineral-hosted fluid inclusions at porphyry deposits are as follows: temperature 90–957 °C, average 388 °C; salinity 0.1–88.0 wt % equiv. NaCl, average 29.4 wt % equiv. NaCl; and density 0.38–1.85 g/cm3, average 0.93 g/cm3. The highest average temperature and the highest maximum homogenization temperatures of the fluids were detected at deposits of the Cu (Au) type, with both values systematically decreasing with the transition to the Cu, Mo (Au), and then to Mo and Au types of porphyry deposits. The situations with the average and maximum salinity values of the fluids and their density are analogous. The data in the literature on the concentrations of some elements are still insufficient to reliably characterize variations in these concentrations at all of the discussed types of porphyry deposits. The highest Cu and Fe concentrations were found in the highest temperature fluids at deposits of the Cu (Au) type. The maximum Mo concentrations were detected in fluids at porphyry Mo deposits, and the highest Ag concentrations occurred at porphyry Au deposits. The chemical composition of the mineralizing fluids is, thus, strongly correlated with the types of the porphyry deposits. The hypothesis is discussed: the geochemical specifics of mineralizing fluids at various types of porphyry deposits of the Cu–Mo–Au system are related to the depths at which fluid separated from the magmatic melt. A scenario is proposed for the separation of mineralizing fluids from granite melt at various depths for fluids that form different types of porphyry deposits.

In the second part of this study, we analyze how crystallization differentiation can affect concentrations of elements and their ratios in melt inclusions and glasses of rocks in major geodynamic environments. The paper presents analysis of experimental data on the partition coefficient of elements between minerals (olivine, pyroxenes, garnet, amphibole, biotite, sulfide, apatite, spinel, ilmenite, rutile, and zircon) and silicate melts, which were discussed in the first part of this study. It is demonstrated that the crystallization of major minerals only insignificantly affects the ratios of incompatible elements. The partition coefficients of some elements between accessory minerals and melts can be very high, but the effects of crystallization differentiation cannot be significant because of the small amounts of the crystallizing phases. These effects are the most significant for chalcophile elements (Cu, Ni, and others), at the separation of sulfides, and for Nb and Ta, at the crystallization of rutile. Differences in concentrations of various elements and their ratios to Cs concentrations are discussed with reference to various geodynamic environments. The maximum values of the ratios of practically all elements to Cs were found in melts in mid-oceanic ridges. The melts of oceanic islands and backarc basins are characterized by relatively low ratios, without any significant anomalies. The lowest ratios of elements to Cs were found in melts of continental and marginal environments. These melts are also characterized by clearly seen geochemical anomalies that are typical of rocks of the corresponding environments (negative Ta–Nb, positive Pb, and other anomalies).

Published data on the composition of mineral-hosted inclusions and quenched glasses of rocks were used to estimate the mean concentrations of 45 volatile, trace, and ore elements in silicate igneous melts from the main geodynamic settings of the Earth and in natural fluids. The following geodynamic settings were distinguished according to the conditions of formation and evolution of the igneous melts: (I) oceanic spreading zones (mid-oceanic ridges), (II) oceanic mantle-plume zones (oceanic islands and lava plateaus); (III and IV) subduction-related settings (III is island-arc zones, and IV is active continental margins); (V) continental rifts and hotspot zones; and (VI) backarc spreading basins related to subduction. The contents of the elements in basic and felsic melts were compared in settings III, IV and V. It was shown that differences in the enrichment factors of ore elements between the geodynamic settings could be caused by variations in the contribution of fluids to element transport and accumulation. Ratios of element contents in each of the geodynamic environments to the global mean values were calculated.

Melt inclusions were investigated in the minerals of dacite tephra of the largest Holocene eruption (7900 years) of Khangar volcano, Sredinny Range of Kamchatka. Melt compositions correspond to rhyolite (SiO2 = 70–77 wt %, Na2O+K2O = 6–7 wt %) with ~5 wt % H2O. The melts show a minor negative Nb anomaly and lesser HREE depletion (La/Yb is ~7.1) compared to those of Ichinsky Volcano, another active volcano of the Sredinny Range of Kamchatka. It was determined that different phenocryst assemblages were formed within temperature ranges of 750–785 and 830–870°C. Evidence for the assimilation of granite-gneiss basement by magmas of Khangar volcano are discussed.

The paper summarizes data on germanium and gallium concentrations in natural magmatic melts as follows from analyses of mineral-hosted inclusions and quench glasses in volcanic rocks. Germanium concentrations in melts vary from 0.96 to 17.6 ppm (1472 determinations). The geometric mean germanium concentration in silicate melts is 1.56 ppm, which is quite close to the clarke value. Concentrations of gallium in magmatic melts vary from 0.47 to 495 ppm (8755 determinations). The geometric mean of gallium concentration in silicate melts is 19.0 ppm, which is also close to the clarke value. Germanium concentration in hydrothermal fluids ranges from 0.01 to 930 ppm (405 determinations), and the geometric mean value is 17.0 ppm. Concentrations of gallium in fluids vary from 0.02 to 320 ppm (441 determinations), with a geometric mean of 2.0 ppm. The possible reasons for the differences in germanium and gallium concentrations in natural melts and fluids are discussed.

The mean concentrations of volatiles, major, and trace elements are estimated in the magmatic melts of Kamchatka based on an our database that includes analyses of melt inclusions and quenched glasses of rocks for 75 elements (the database comprised 1 900 000 analyses as of late 2018). The determined concentrations are compared with analogous characteristics of melts from island arcs and active continental margins. The distribution of SiO2 concentrations (more than 105 000 analyses) in natural magmatic melts from all geodynamic environments is obviously bimodal, with maxima at SiO2 = 50–52 and 72–76 wt %. The paper presents binary diagrams that show the concentrations of major, volatile, trace elements, and REE and diagrams of the normalized patterns average concentrations of elements in the magmatic melts. The diagrams show distinguishing features of the melts of Kamchatka, for example, the elevated Ba/Nb ratios of Kamchatka mafic melts compared to those of melts in other zones, which may reflect a high content of subduction-related material during the derivation of the Kamchatka melts, with their Th deficit controlled by specifics of the fluid regime.

Authors’ original continuously updated database, which currently comprises data from 22 300 publications on mineral-hosted fluid and melt inclusions, is used to generalize data on the physicochemical parameters of processes that produced fluorite and barite deposits. The paper presents data on the following parameters of the fluids: temperature, pressure, density, salinity, and gas composition. The average composition (Н2О, CO2, CH4, N2, H2S, and CnHm) of fluids at fluorite–barite deposits is calculated. The paper reports the average composition of major gas components (CO2, CH4, N2, and H2S) of natural fluids at these deposits on the basis of Raman spectroscopic analyses of individual inclusions. Average F, S, and Ba concentrations are calculated for silicate magmatic melts and natural mineral-forming fluids.

The inclusions of a silicate melt were investigated in quartz insets of the extrusive rhyolite collected at Bazman Cenozoic volcano (Iran) and associated with the process of recent subduction. Low temperatures of the silicate melt along with high concentrations of water in the melt are ascertained. The microelemental composition of the melt showed a similarity to acidic melts of island-arc formations.

The paper reports data on glassy melt inclusions in minerals of tephra that was produced by the most significant eruptions of Ichinsky volcano, Kamchatka, and marked the major evolutionary stages of the volcanic center in the Pleistocene–Holocene. The melts are of dacite–rhyodacite composition (68–77 wt % SiO2, 0.1–0.6 wt % MgO) and contain 2–4 wt % H2O (3.3 wt % on average). Most of the melts are potassic (3.8–4.8 wt % K2O), but some of them are less alkaline (2.5 wt % K2O) and richer in iron and calcium. The trace-element composition of the glasses also suggests the presence of melts of two types. The high-K melts are relatively deficient in Nb and HREE (Nb = 10–14 ppm, La/Yb = 10–20), whereas the low-K melts typically show more clearly pronounced Nb minima, are relatively depleted in LREE, and are enriched in HREE (Nb = 3–4 ppm, La/Yb = 3–5). The two melt types likely sampled a long-lived magmatic chamber and, perhaps, also one of the components of magmatic mixing, whose addition to the system may have provoked the beginning of a reactivation stage of the volcanic center.